Burglar alarm system having plural vibration detectors with actuation indicators



MELMHMH MUMWB July 21, 1970 HALL 3,521,266

BURGLAR ALARM SYSTEM HAVING PLURAL VIBRATION DETECTORS WITH ACTUATIONINDICATORS Original Filed May 17, 1967 ALARM INVENTOR. ROBERT A. HALLEM- -J A ATTORNEYS United States Patent M 3 521,266 BURGLAR ALARM SYSTEMHAVING PLURAL VIBRATION DETECTORS WITH ACTUATION INDICATORS Robert A.Hall, Montclair, N.J., assignor to Guardian Industries, Inc.,Springfield, N..I., a corporation of New Jersey Original application May17, 1967, Ser. No. 639,181, now Patent No. 3,392,246, dated July 9,1968. Divided and this application May 1, 1968, Ser. No. 725,757

Int. Cl. G08h 13/02 US. Cl. 340-261 1 Claim ABSTRACT OF TI-m DISCLOSUREA burglar alarm system comprises a plurality of vibration detectiondevices mounted on one or more surfaces to be protected at a pluralityof spaced-apart locations to detect vibration thereof. An alarm incircuit with the devices responds to actuation of any one of thedevices. Each of the vibration detection devices includes an actuatorfor actuating such device upon the occurrence of vibrations exceeding apredetermined intensity. In addition, the actuating means maintains suchactuated device in an actuated condition to facilitate identification ofthe actuated device among a plurality of devices. The devices aremanually engageable for resetting.

CROSS-REFERENCE TO RELATED APPLICATION This is a division of mycopending application Ser. No. 639,181, filed May 17, 1967, now Pat. No.3,392,246, for Vibration Detection Device.

BACKGROUND OF THE INVENTION Field of the invention This inventionrelates to a burglar alarm system and, in particular, to a novel andhighly-improved burglar alarm system including a plurality of devicesthe sensitivity of each of which is adjustable independently of theforce with which first and second break contacts are normally pressedtogether. Means are provided for maintaining each device of the systemin such condition following actuation as to facilitate readyidentification of the device as having been actuated.

Description of the prior art Vibration detectors are known and are used,for example, for burglary detection. In such use, vibration detectorsare typically mounted on windows, doors, or walls and are designed toopen momentarily normally-closed electrical contacts when vibrationresults from an attempt to break through the protected surface.Conventional vibration detectors have, however, a number of seriousdisadvantages. For example, they are typically prone to produce false orspurious alarms after installation, and their design is such that it isextremely diificult to locate the malfunctioning detector or detectorsin a typical multidetector burglar alarm installation.

One reason for the difliculty in detecting an improperly adjusted deviceis that the contacts opened by, for exam ple, nearby vehicular trafficpromptly close again after the passage of the disturbance so thatinspection of the devices fails to reveal which of them actuated thealarm.

Another shortcoming of conventional devices is that the force with whichthe contacts are normally held together is a function of the adjustmentof the sensitivity. For a sensitive adjustment, a light force isnecessary, which means that dry circuit phenomena including resistiveox- 3,521,266 Patented July 21, 1970 SUMMARY OF THE INVENTION An objectof the present invention is to remedy the shortcomings noted above. Inparticular, an object of the invention is to provide a burglar alarmsystem comprising a plurality of rugged, simple, inexpensive, compactvibration detection devices in which the relatively movable contacts arestrongly held in their normal relative posi tions irrespective of thesensitivity adjustment and which, once actuated, remain in a conditionadapted to facilitate ready verification of the fact of actuation.

The foregoing and other objects are attained in accordance with theinvention by the provision of a burglar alarm system comprising aplurality of vibration detection devices mounted on surfaces at aplurality of spacedapart locations to detect vibration thereof and alarmmeans in circuit with such devices responsive to actuation of any one ofsuch devices to produce an alarm, the vibration detection devicesrespectively including a plurality of actuating means for (a) actuatingthe respective devices upon the occurrence of vibrations of therespective surfaces exceeding predetermined intensities and (b)maintaining the actuated devices in an actuated condition, to facilitateidentification of actuated devices without employment of separate alarmcircuits therefor. Manually engageable means is provided for resettingthe devices.

BRIEF DESCRIPTION OF THE DRAWING An understanding of other aspects ofthe invention may be gained from a consideration of the followingdetailed description of representative embodiments of the invention andof the accompanying figures of the drawing, in which:

FIG. 1 is a side elevational view, partly in section, of an exemplaryembodiment of a device suitable for use in accordance with theinvention;

FIG. 2 is a fragmentary perspective View, on an enlarged scale, of theapparatus of FIG. 1;

(FIG. 3 is a fragmentary elevational view, on the same scale as FIG. 1,of the apparatus of FIG. 1 in an actuated condition; and

FIG. 4 is a schematic diagram of a plurality of devices according toFIGS. 13 in an alarm circuit according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows apparatus 10constructed in accordance with my copending application identifiedabove. The ap paratus includes an insulating base 12 mounted on asurface 14 to be protected. The surface 14 is typically the surface of awall, door, window, floor, or ceiling.

A first electrically conducting strip, which may be of brass, is mountedon the insulating base 12. The electrically conducting strip 16 has aterminal portion 18 and a contact portion 20. The terminal portion 18 iselectrically connected to a lead 22 by a terminal screw 24. The contactportion 20 of the strip 16 is preferably formed with a contact 26 whichis normally closed with a second contact 28.

The contact 28 is formed on a second electrically conducting member 30,which may also be of brass. The conducting member 30 is preferably aflexible spring mounted in cantilever fashion, the free end 32accommodating the contact 28 and the other end 34 being supported by aninsulating mounting 36 in insulated relation from the conducting strip16 and serving as a second terminal portion.

A terminal screw 38 connects a second electrically conducting lead 40 tothe portion 34 of the spring 30-.

The contacts or contacting portions 26 and 28 and normally pressedfirmly together so that minor heating or warping of the surface 14 orthe formation of oxides on the contacts will not cause the generation ofspurious signals. The spring 30 is not provided with a weight, as intypical conventional devices, so the contact 28 tends to follow thevibration of the surface 14 just as does the contact 26.

Actuation of the device to separate the contacts 26 and 28 is effectedby a biased lever 42. The biased lever is pivotally mounted and biasedby means such as a tension coil spring 44. The upper end 46 of the leveris normally retained by a notch 48 formed in a leaf spring 50. Thoseskilled in the art will readily understand that other retaining meanscan be employed in lieu of the notch 48. For example, the lever 42 couldbe provided with pins insertable within holes formed in the spring 50.

As FIG. 2 best shows, the spring 44 is anchored at its lower end 44a ina boss 12a formed on a plate 12b securely attached to the base 12. Atits upper end 44b, the spring 44 is secured through an eye 42a formed ina tab 42b on the lever 42. A wall portion 120 integral with the plate12b is formed with a slot 12d permitting pivoting movement of the lever42, as will hereinafter become evident.

The notched spring 50 tends to remain stationary notwithstandingvibration of the surface 14 because of the inertia of a weight 52mounted thereon. The position and, if desired, the magnitude of theweight 52 are adjustable to adjust the sensitivity of the device. Inaddition, the sensitivity of the device is adjustable by a threadedscrew 54 adapted to bear on the spring 50 at a point 56. The spring 50is flexible, and the force with which the screw 54 bears on the spring50 adjusts the tendency of the notch 48 to follow downward movement ofthe lever 42 as seen in FIG. 1.

The adjustment screw 54 is mounted in a threaded aperture 58 formed in aspring retainer 60. The spring retainer '60 and the end 62 of the spring50 are secured by the terminal screw 38 to the insulating mounting 36.

A dust cover 64, preferably formed of an insulating material, forms asnap-on engagement at 66 with the base 12 and protects the apparatusfrom dust.

The dust cover 64 is formed with a slot 68, and the lever 42 has aprotruding portion 70 which extends exteriorly of the dust cover 64 tofacilitate manual engagement for resetting the device after actuation.The protruding portion 70 of the lever 42 also facilitates readyverification of the fact that a device has been actuated and makes itpossible to identify one or more vibration detection devices of aplurality of such devices arranged in circuit with an alarm which may begenerating spurious alarm signals.

Specifically, in operation, when the surface 14 and base 12 vibrate, theportion 46 of the lever 42 (see especially FIG. 2) engaging the notch 48in the spring 50 will, if the intensity of the vibration exceeds apredetermined magnitude which is a function of the position and mass ofthe weight 52 and of the adjustment of the screw 54, move out ofengagement with the notch 48, so that the spring 44 pivots the lever 42clockwise as seen in FIG. 1 and the end 72 separates the contacts 26 and28, as shown in FIG. 3.

Inasmuch as the lever 42 remains in the actuated condition shown in FIG.3 until it is reset, the portion extending at an angle of about 45 tothe horizontal, the fact that the device has been actuated is readilydetermined upon visual inspection.

In accordance with the present invention, a plurality of such devices A,B, C, and N is arranged in circuit with an alarm 74 between leads 76 and78. If experience shows that one of the devices is adjusted so that itrepeatedly gives a spurious indication of an attack upon the protectedsurface, the device may be rendered less sensitive by adjustment of thescrew 54. Any detector which has been actuated can be manually reset bymanual engagement of the portion 70 of the lever 42 to move the lever 42to a position normal to the base member 12.

Thus there is provided in accordance with the invention a novel andhighly-eifective burglar alarm system. The apparatus of the invention isrugged, simple, compact, and inexpensive to manufacture and repair. Arelatively large contact force of, say 12 to 20 grams may be providednotwithstanding a very sensitive adjustment of the device.

Many modifications within the spirit and scope of the invention of therepresentative embodiments disclosed herein will occur to those skilledin the art. For example, vibration detectors, other than the onespecifically illustrated, may be employed in accordance with theinvention. Accordingly, the invention is to be construed as includingall of the embodiments thereof within the scope of the appended claim.

"I claim:

1. A burglar alarm system comprising a plurality of vibration detectiondevices mounted on surfaces at a plurality of spaced-apart locations todetect vibration thereof and alarm means in circuit with said devicesresponsive to actuam'any one of said devices to produce an alarm, eachof said vibration detection devices including a lever, each of saidlevers (a) actuating the vibration detection device with which it isassociated upon the occurrence of vibrations of the surface protected bysaid device exceeding a predetermined intensity and (b) maintaining saidactuated device in an actuated condition, said levers being mounted tobe visible at least in part from outside said respective devices and theappearance of said levers facilitating identification of actuateddevices among said plurality of devices without employinent of separatealarm circuits therefor, and said levers respectively including portionsmanually engageable for resetting said devices.

References Cited UNITED STATES PATENTS 640,273 1/ 1900 Coleman.1,192,312 7/1916 Hopkins 340-261 1,903,584 4/ 1933 Wettengel. 2,942,4566/ 1960 Hardway 73-71 3,333,073 7/ 1967 Ohlson ZOO-61.45

JOHN W. CALDWELL, Primary Examiner D. L. TRAFTON, Assistant Examiner US.Cl. X.R. 340-276

